Single Fiber Wettability in PET Fibrous Assembly Exposed to Atmospheric Pressure Plasma

Poly (ethylene terephthalate), PET, fibrous assembly was treated by atmospheric pressure plasma (APP) jet with three different reactive gas sources, air, nitrogen and argon. The change in the wettability of single fiber surface due to the treatment was determined by the wetting force measurement with moving the fiber/water/air three-phase boundary. Both advancing and receding contact angles of water on the PET fiber decreased considerably by the APP treatment, even if the hydrophobic recovery of the treated fiber surface after the aging in air and rinsing with water was taken into consideration. The contact angles on a treated single fiber surface showed periodic variation along the fiber axis, indicating that the fiber surfaces were not treated uniformly because of fiber crimps due to the structure of the fibrous assembly. The water wicking into the capillaries of the fibrous assembly was promoted after the APP treatment, in good agreement with single fiber wettability. From X-ray photoelectron spectroscopy and atomic force microscopy, the oxygen concentration and the roughness on the PET fiber surface were found to enhance after the APP treatment. The above changes in the surface properties of a single fiber were remarkable for using nitrogen as a reactive gas.